Complexes of [Ph(2)P(O)NP(E)Ph(2)](-) (E=S or Se): Disparate ring conformations within a new palladacycle

A new mixed oxygen-selenium ligand Ph(2)P(O)NHP(Se)Ph(2), its potassium salt K[Ph(2)P(O)NP(Se)Ph(2)] and the bis(chelate) palladium (II) complex cis-[Pd{Ph(2)P(O)NP(Se)Ph(2)-O,Se}(2)] have been prepared. In cis-[Pd{Ph(2)P(O)NP(Se)Ph(2)-O,Se}(2)] the two cis six-membered Pd-O-P-N-P-Se rings adopt different conformations: one is a pseudo-boat whilst the other is chair-like (X-ray evidence). Reaction of 2 equivalents of K[Ph(2)P(O)NP(Se)Ph(2)] with [PtCl2(cod)] (cod = cycloocta-1,5-diene) in MeOH, or more conveniently using the methoxo-bridged platinum(II) dimer [{Pt(mu-OMe)(C(8)H(12)OMe)}(2)] (C(8)H(12)OMe = 8-methoxycydooct-4-en-1-yl), afforded [Pt(C(8)H(12)OMe){Ph(2)P(O)NP(Se)Ph(2)-O,Se}] as one isomer only. The mixed oxygen-sulfur salt K[Ph(2)P(O)NP(S)Ph(2)] was used to prepare similar compounds, all of which have been characterised by a combination of multinuclear NMR (P-31-{H-1}, Pt-195-{H-1} and H-1), IR spectroscopy and microanalysis. The molecular structures of Ph(2)P(O)NHP(S)Ph(2), cis-[Pd{Ph(2)P(O)NP(Se)Ph(2)-O,Se}(2)] and[Pt(C(8)H(12)OMe){Ph(2)P(O)NP(S)Ph(2)-O,S}] have been determined by single-crystal X-ray diffraction.